title: Tribolayer formation in a metal-on-metal (MoM) hip joint: an electrochemical investigation.
abstract: The demand for total hip replacement (THR) surgery is increasing in the younger population due to faster rehabilitation and more complete restoration of function. Up to 2009, metal-on-metal (MoM) hip joint bearings were a popular choice due to their design flexibility, post-operative stability and relatively low wear rates. The main wear mechanisms that occur along the bearing surface of MoM joints are tribochemical reactions that deposit a mixture of wear debris, metal ions and organic matrix of decomposed proteins known as a tribolayer. No in-depth electrochemical studies have been reported on the structure and characteristics of this tribolayer or about the parameters involved in its formation. In this study, we conducted an electrochemical investigation of different surfaces (bulk-like: control, nano-crystalline: new implant and tribolayer surface: retrieved implant) made out of two commonly used hip CoCrMo alloys (high-carbon and low-carbon). As per ASTM standard, cyclic polarization tests and electrochemical impedance spectroscopy tests were conducted. The results obtained from electrochemical parameters for different surfaces clearly indicated a reduction in corrosion for the tribolayer surface (Icorr: 0.76μA/cm(2)). Further, polarization resistance (Rp:2.39±0.60MΩ/cm(2)) and capacitance (Cdl:15.20±0.75μF/cm(2)) indicated variation in corrosion kinetics for the tribolayer surface, that attributed to its structure and stability in a simulated body environment.
authors.affiliation: (a)Section of Tribology, Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL-60612, USA. Electronic address: mathew_t_mathew@rush.edu.
authors.forename: M T
authors.initials: MT
authors.lastname: Mathew
authors.forename: C
authors.initials: C
authors.lastname: Nagelli
authors.forename: R
authors.initials: R
authors.lastname: Pourzal
authors.forename: A
authors.initials: A
authors.lastname: Fischer
authors.forename: M P
authors.initials: MP
authors.lastname: Laurent
authors.forename: J J
authors.initials: JJ
authors.lastname: Jacobs
authors.forename: M A
authors.initials: MA
authors.lastname: Wimmer
mesh_terms: D000497:Alloys / Q000737:chemistry; D002244:Carbon / Q000737:chemistry; D003343:Corrosion; D004563:Electrochemistry; D006621:Hip Joint; D053768:Metal Nanoparticles / Q000737:chemistry; D019216:Metals, Heavy / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D000497:Alloys; D019216:Metals, Heavy; D002244:Carbon
keywords: CoCrMo alloy; Corrosion kinetics; Electrochemistry; MoM hip implant; Tribolayer